Mechanical fasteners are known in the art. Such fasteners are often called “hook and loop” fasteners. One popular type of mechanical fastener is sold under the trade name Velcro®. Mechanical fasteners permit repeated fastening and unfastening of components having the fastener. In practice, one portion of the component to be fastened has the “hook” members, referred to as the “male” fastener component. Another portion of the component to be fastened has a mating “loop” member, referred to as the “female” fastener component. The hooks and loops are flexible and resilient, such that when pressed together the hooks of the male fastener component engage the loops of the female fastener component in a manner that provides for a certain resistance to release by shear and/or peel forces. The actual amount of resistance depends on a variety of design factors, such as type of loop material, type of hook material, number of hooks (e.g., per unit area), number of loops available for catching by hooks, and the like.
Mechanical fasteners find use in a wide variety of articles, including clothing, sports equipment, industrial equipment, consumer goods, and virtually any item that benefits from repeated opening and closing. One example of clothing, for example, is shoes, where mechanical fasteners often replace shoelaces as a means for secure closure. Mechanical fasteners are also used on disposable articles, such as packaging, medical gowns and disposable diapers as a means for providing for repeated opening and closing.
Much effort has been expended in an effort to provide a more consumer-acceptable mechanical fastener. Consumer acceptability depends on the end use, but in general consumer acceptance for disposable articles can be improved by reducing the cost of the fastener and increasing its reliability. However, a technical contradiction exists between such cost reduction and the desire to increase reliability. For example, woven, knit, and nonwoven webs are known materials useful for female fastening components. Woven and knit materials can be made to provide relatively high reliability due to the ability to make effective loop structures but are relatively high cost materials. Nonwoven materials are significantly less costly to produce, but exhibit significantly less reliability for use as the loop portion of a mechanical fastening member. That is, in general, even with optimized mating hook portions, nonwoven web loop materials exhibit less resistance to peel and shear forces than those exhibited by woven or knit loop materials, and thereby exhibit relatively less reliability as a fastener.
One reason nonwoven webs are less reliable than woven or knit materials as a hook component of a mechanical fastener is the lack of integrity of the “loops” in a nonwoven, that is, the fiber portions available for engaging with a hook member. In a woven or knit material each loop is substantially anchored to resist pulling apart when a mating hook member is disengaged. However, for nonwoven webs, the loops formed by randomly distributed fibers are not necessarily anchored to resist such pulling apart. Therefore, upon disengaging of a hook member, the hook tends to pull fibers loose. The ease with which the fibers can be pulled loose is one factor in determining the peel and shear forces necessary to unfasten the fastener. The number of fibers that get pulled loose is also a factor in determining whether the fastener can be used repeatedly. This problem is especially significant for low basis weight nonwoven webs.
One way to improve the integrity of a nonwoven web is to increase the amount of bonding of the constituent fibers. For example, a nonwoven web can be bonded to a backing layer in known ways, such that constituent fibers are bonded, or anchored to the backing layer. By increasing the bond area, more fibers can be anchored to the backing. However, increasing the bond area also increases the number of fibers that are not available for hook engagement. At 100% bond coverage, for example, each fiber would be anchored to avoid pulling away from the web, but there would be no fibers available for hook engagement.
Attempts have been made to make hook members that are less costly and work well with nonwoven web loop members. For example, U.S. Pat. No. 5,058,247, issued Oct. 22, 1991 to Thomas et al., teaches engaging means in the form of hook-shaped tine for securing in engaging means having strands and fibers. However, there is no teaching in Thomas et al. directed to the optimization of the engaging means, such as a nonwoven web loop member.
Attempts to optimize the nonwoven web loop member have also been made. For example, U.S. Pat. No. 5,595,567 teaches utilizing predetermined patterns of bonding pattern elements on the nonwoven that intersect predetermined construction bonds that join the nonwoven to an elongatable backing. However, this structure requires an elongatable backing, which must have a relaxed orientation, such as an elastomeric material, for example. Therefore, while reliability may be increased, cost is not sufficiently decreased for many applications of disposable articles.
Accordingly, it would be desirable to have a nonwoven loop member for a mechanical fastener with increased fastening reliability.
Additionally, it would be desirable to have a nonwoven loop member for a mechanical fastener with increased fastening reliability that can be made in a commercially viable manner.
Further, it would be desirable to have a nonwoven loop member for a mechanical fastener with increased fastening reliability that does not require a backing material having relaxed orientation.
Finally, it would be desirable to devise a nonwoven loop material for a mechanical fastener having a bond pattern that bonds relatively more fibers without a corresponding significantly increased bond area.